In rail vehicles, a traction device is generally used to transmit a longitudinal load between a vehicle body and a bogie. At present, a conventional traction device mainly includes two types of traction devices: a single traction bar type and a Z-shaped double traction bar type. The two types of traction devices are both connected to a center pin and a bogie frame through a traction bar having rubber joints at two ends. The traction bar, as a connecting mechanism between the vehicle body and the bogie, is apt to become a transmission path of harmful vibrations. According to research, the stiffness of the traction bar is closely related to the comfort degree of vibration of the vehicle body. Therefore, some joints employ a structure provided with a gap to achieve a nonlinear stiffness. However, since the gap may be adversely affected by the size of the joints, reliability and stability of the gap, the stiffness property of such structure cannot fully meet the design requirements, and under alternating loads, fatigue damage may occur to the rubber joints at the two ends of the traction bar.